title: Decoupling factors affecting plant diversity and cover on extensive green roofs.
abstract: Supplemental irrigation systems are often specified on green roofs to ensure plant cover and growth, both important components of green roof performance and aesthetics. Properties of the growing media environment too can alter the assemblage of plant species able to thrive. In this study we determine how plant cover, above ground biomass and species diversity are influenced by irrigation and growing media. Grass and forb vegetative cover and biomass were significantly greater in organic based growing media but there was no effect of supplemental irrigation, with two warm season grasses dominating in those treatments receiving no supplemental irrigation. On the other hand, plant diversity declined without irrigation in organic media, and having no irrigation in inorganic growing media resulted in almost a complete loss of cover. Sedum biomass was less in inorganic growing media treatments and species dominance shifted when growing media organic content increased. Our results demonstrate that supplemental irrigation is required to maintain plant diversity on an extensive green roof, but not necessarily plant cover or biomass. These results provide evidence that planting extensive green roofs with a mix of plant species can ensure the survival of some species; maintaining cover and biomass when supplemental irrigation is turned off to conserve water, or during extreme drought.
authors.affiliation: Biology Department, York University, 4700 Keele St., Toronto, ON M3J 1P3, Canada; Green Roof Innovation Testing (GRIT) Lab, Daniels School of Architecture, Landscape, and Design, University of Toronto, 230 College St., Toronto, ON M5T 1R2, Canada. Electronic address: jsmacivor@gmail.com.
authors.forename: J Scott
authors.initials: JS
authors.lastname: MacIvor
authors.forename: Liat
authors.initials: L
authors.lastname: Margolis
authors.forename: Curtis L
authors.initials: CL
authors.lastname: Puncher
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Carver Matthews
mesh_terms: D057914:Agricultural Irrigation; D044822:Biodiversity; D018533:Biomass; D003247:Conservation of Natural Resources / Q000379:methods*; D006109:Poaceae / Q000502:physiology*
keywords: Diversity; Green infrastructure; Growing media; Irrigation; Sedum; Vegetative cover